Recycling of Polluted Dredged Sediment – Building New Materials for Plant Growing

The worldwide concern is caused by a large quantity of dredged sediment. The issue becomes more severe when contaminated sediment has to be landfilled. Therefore, researchers involved in the dredged sediment management are increasingly motivated to improve circularity in sediment management processes. Prior to the dredged sediment usage in agriculture, its necessary to confirm conclusively its safety in the context of trace elements (TEs) levels. This study reports the use of different solidification/stabilization (S/S) sediment amendments (cement, clay, fly ash and green synthetized nano-zerovalent iron-nZVI) to remediate dredged sediment. The aim was to identify the effects of applied sediment S/S treatments on the growth and development of Brassica napus. The results showed that in all S/S mixtures TEs levels in the highly labile and bioavailable fraction were significantly decreased (less than 10%, while untreated sediment contained up to 36% of TEs). Simultaneously, the highest share of metals (69-92%) was in the residual fraction, which is considered as chemically stable and biologically inert fraction. Nevertheless, it was noticed that different S/S treatments trigger plants' functional traits indicating that plants' establishment in S/S treated sediment can be limited to certain extent. Besides, based on primary and secondary metabolites (elevated specific leaf area along with declined malondialdehyde content) it was concluded that Brassica plants employ a conservative resource use strategy aiming to buffer phenotypes against stress condition. Lastly, it was inferred that among all analyzed S/S treatments, green synthetized nZVI from oak leaves can effectively promote TEs stabilization in dredged sediment, concurrently enabling plant's establishment and fitness.